Vents cool only 65-67 degrees?

[joe 40]

Need help. Just installed new 3 ton for 1300sf home.(I know, oversized slightly) but wanted to cool home faster and colder. Old unit wouldn't cool home. I also don't have enough insulation in house.

Why doesn't the air out of the vents come out cold? Have temp. set at 77 on a 98degree day. Intake says 77degree but air out of vents only 67. That's a 10degree difference. Any one know why?

System is a Goodman 3 ton,14 seer. Tech says this is normal for a 14 seer. True?

[Edited by joe 40 on 08-21-2005 at 05:14 PM]

[mark beiser]

It is not normal if the humidity is low or normal in the house. A 10º temperature drop could indeed be normal if the humidity level is high very high in the house, but generally I would only expect to find a 10º split on a system when it is very hot and somewhat humid in the house, not when the RA temperature is below 80º.

There are many things that can cause your problem, none of wich anyone can make an educated guess at with the information provided.

With an oversized 14 SEER system with fixed metering, you are going to have some real problems with humidity control, even once the system is operating properly.

[dan sw fl]

Originally posted by joe 40
Need help. Just installed new 3 ton for 1300 S.F. home.
(I know, oversized slightly) but wanted to cool home faster and colder. Old unit wouldn't cool home.
I also don't have enough insulation in house.

Why doesn't the air out of the vents come out cold?
Have temp. set at 77 on a 98 degree day.
Intake says 77 degree but air out of vents only 67.
That's a 10 degree difference. Any one know why?
[Edited by joe 40 on 08-21-2005 at 05:14 PM]

I would say 3 tons for 1,300 S.F. is
MORE than slightly oversized.


Joe,
Check temp directly at Air Handler outlet.

If air handler outlet temp is <_ 62'F,
your duct is not providing the best performance.
With 98'F outside temperature is the attic > 140 degrees.
Are the ducts located in the attic?

Keep searching for root cause
because with low air flow (~1,000 CFM) Minimum Delta T across air handler should be at least 20'F.
77'F - 57'F out AT air handler.

Best of luck and patience!

[joe 40]

Ducting is in the attic and no it can't be more than 130 degrees cause I installed an electric exhaust fan. It's set at 110.

Do you think I should have gotten a 2 1/2 ton? That's what I took out cause tech told me it was too small!!
What kind of humidity should I have if I have the temp at 77 degrees. Is 54% high? Outside temps are like 98-100.

[atufano]

Originally posted by joe 40
Ducting is in the attic and no it can't be more than 130 degrees cause I installed an electric exhaust fan. It's set at 110.

Do you think I should have gotten a 2 1/2 ton? That's what I took out cause tech told me it was too small!!
What kind of humidity should I have if I have the temp at 77 degrees. Is 54% high? Outside temps are like 98-100.

Is it a fixed orifice or txv?

Just because your fan is set at 110 doesn't mean that it's 110. That fan cannot move that many CFM to keep the attic that cool. It is very possible that you attic can reach 140 in many areas of your attic. Just not near your t-stat, which are usually located near the fan.

Was a manual J done on your home?

[beenthere]

give the mod numbers of the outdoor, and indoor unit, if the indoor is a mod, give the coil number also.

Doesn't goodman use a 5 ton coil on the 3 ton high seer stuff.

[BaldLoonie]

What did the heat load calc on the house call for?

[dhvac]

just a thought but did anyone check the air filter?

i know its a new a/c but does not mean that they checked it


also did they change the whole system or just the condensing unit?

[joe 40]

Filter new.
Whole thing was changed inside and out. Brand new ducting too. Spend a fortune and still not working!!

No heat load done, but last unit would run all day to cool house and it was a 2 1/2. Yes, they say it should run like that but paid electric bill of 288!!

[atufano]

Originally posted by joe 40
Filter new.
Whole thing was changed inside and out. Brand new ducting too. Spend a fortune and still not working!!

No heat load done, but last unit would run all day to cool house and it was a 2 1/2. Yes, they say it should run like that but paid electric bill of 288!!

$288? There is a reason why they call it comfort cooling. My bill was $224. I live in a 800 2ft home. It was also over 90 for many days. But it kept my house at 75..

Call back the company that installed the system and have them explain or fix why your new system is not working. Sounds like it could be an installation realted problem.

Ask them to also provide you with the reason they chose 3 tons.

Click on the bullseye on the top of the page, pay 50 bucks and then you'll know what size unit you should have in your home.

[joe 40]

Temp was only set at 78degrees! 3 hundred a little too much for my pocket.

[dan sw fl]

Originally posted by joe 40
Do you think I should have gotten a 2 1/2 ton? That's what I took out cause tech told me it was too small!!
What kind of humidity should I have if I have the temp at 77 degrees. Is 54% high? Outside temps are like 98-100.

54% is good for most areas.

Location ? ____

[joe 40]

Live in South Texas.Would love to feel cold air coming out of vents instead of just cool.

[r2]

my guess would be that he didn't use a charging chart when charging your system and now you're slightly undercharged. '
or perhaps a txv was mistaken for a orifice, but before you go any further stick that temp prope in your supply plenum and read the temp of that. when that's done put it in the return.

[cem-bsee]

what is the temp in the house when outside is 95F? what RH%?

machinery running all the time usually is at or near full effeciency! starting & stopping shortens machinery life.

[docholiday]

Whats the airflow? Chances are no one has even considered this. Rarely is it too much but it could be. High airflow could also cause a low temperature drop. High humidity, which also seems to be missing from the data will cause low temperature splits. Leaking ductwork pulling in attic air is also culprit. Low airflow can cause a tech to overcharge the unit which will reduce the capacity of the machine.

77 degrees where? At the inlet of the coil or at the return grille? 67 where? At the outlet of the plenum or at the registers.

What was your electrical usage last year? Has the rate gone up? Have the degree days gone up? Its too bad you didnt have a load calc or anyone look for infiltration air.

[joe 40]

Supply is 77degrees and return(vents?) is 67degrees

Outside temp97 outside humidity 78.
Inside temp 77 inside humidity 56.

Air handler has high air flow should I slow it down?

System is running like 40minutes on and 18off. House is cool but still I feel the vents should give me below 60 degrees.

[docholiday]

Lets assume you have some gain in your ducts of even 2 degrees in both return and supply. That would be 79 return at the unit and 65 at the outlet of the coil. Thats a 14 degree split. High humidity along with too much airflow is going to make that so. We dont know the airflow so I dont suggest messing with it. A good tech ought to be able to properly troubleshoot it. Arbitrarily lowering the airflow can cause compressor damage among other problems.

[dan sw fl]

Originally posted by joe 40 Air handler has high air flow should I slow it down?

System is running like 40 minutes on and 18 off.

Maybe, but you have not provided the the current air handler Plenum temperature and air flow, Have you?

What is 'High' air flow?

If the air flow is slowed down,
will the air handler and plenum be more
susceptible to sweating?

I assume the run time applies to the Afternoon (~11 AM to ~7 PM). It appears that this system is slightly oversized, with 56% R.H. and moderate to lower-than-normal run times.

[Edited by dan sw fl on 08-22-2005 at 09:41 AM]

[joe 40]

Thanks for replying but I'll just wait for the a/c tech if he ever gets here. Wife is getting inpatient cause she wants cold air out of the vents!